Regulation of the epithelial Na+ channel by paraoxonase-2

J Biol Chem. 2017 Sep 22;292(38):15927-15938. doi: 10.1074/jbc.M117.785253. Epub 2017 Aug 2.

Abstract

Paraoxonase-2 (PON-2) is a membrane-bound lactonase with unique anti-oxidative and anti-atherosclerotic properties. PON-2 shares key structural elements with MEC-6, an endoplasmic reticulum-resident molecular chaperone in Caenorhabditis elegans MEC-6 modulates the expression of a mechanotransductive ion channel comprising MEC-4 and MEC-10 in touch-receptor neurons. Because pon-2 mRNA resides in multiple rat nephron segments, including the aldosterone-sensitive distal nephron where the epithelial Na+ channel (ENaC) is expressed, we hypothesized that PON-2 would similarly regulate ENaC expression. We observed PON-2 expression in aquaporin 2-positive principal cells of the distal nephron of adult human kidney. PON-2 also co-immunoprecipitated with ENaC when co-expressed in HEK293 cells. When PON-2 was co-expressed with ENaC in Xenopus oocytes, ENaC activity was reduced, reflecting a reduction in ENaC surface expression. MEC-6 also reduced ENaC activity when co-expressed in Xenopus oocytes. The PON-2 inhibitory effect was ENaC-specific, as PON-2 had no effect on functional expression of the renal outer medullary potassium channel. PON-2 did not alter the response of ENaC to extracellular Na+, mechanical shear stress, or α-chymotrypsin-mediated proteolysis, suggesting that PON-2 did not alter the regulation of ENaC by these factors. Together, our data suggest that PON-2 regulates ENaC activity by modulating its intracellular trafficking and surface expression.

Keywords: Caenorhabditis elegans (C. elegans); Paraoxonase; Xenopus; aldosterone sensitive distal nephron; epithelial sodium channel (ENaC); lactonase; molecular chaperone; sodium channel.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Animals
  • Aryldialkylphosphatase / metabolism*
  • Caenorhabditis elegans Proteins / metabolism
  • Conserved Sequence
  • Epithelial Sodium Channels / chemistry
  • Epithelial Sodium Channels / metabolism*
  • Evolution, Molecular
  • Gene Expression Regulation
  • HEK293 Cells
  • Humans
  • Kidney Tubules, Distal / metabolism
  • Mice
  • Oocytes / metabolism
  • Protein Subunits / metabolism
  • Rats

Substances

  • Caenorhabditis elegans Proteins
  • Epithelial Sodium Channels
  • Protein Subunits
  • MEC-6 protein, C elegans
  • Aryldialkylphosphatase
  • PON1 protein, human
  • PON2 protein, human